Ideal Size of an Online Community

Email Article |  digg it |  reddit |  delicious |  StumbleUpon |  Facebook |  Twitter |  LinkedIn 

Last week, a prospect who was interested in our online community software asked me what the best size of an online community was.  I wanted to reply "150.2 members," but I realized it was a joke only a few of my friends would get.   

The 150 is Dunbar's number, popularized by Malcolm Gladwell's book The Tipping Point. Robin Dunbar, a British evolutionary biologist, looked at the tribe size of non-human primates and estimated that humans could maintain stable social relationships with approximately 150 people.  This number has been twisted to many uses beyond its original purpose.  Some have used it to argue that 150 is the ideal size of an online community, but I don't believe that primate tribes, which are organized by instinct and for survival, are applicable to online communities, even if some members act like monkeys sometimes!

So that's the reference to 150.  As to the 0.2... 

Years ago, on a romantic walk on Humarock Beach with my then girlfriend (now my wife), the subject strayed to children.  I asked her how many children she wanted to have.  Her answer:  "2.2.  Somebody has to have the average."

This was a rare geeky quip from my wife, who is anything but a geek. So, 150.2 members is not the ideal community size.  What is?  Well, my actual answer to the prospect was something like, "There is no ideal number, no one-size-fits-all.  It depends on the purposes of your community."

Some community software vendors advocate only small communities.  Others advocate only large communities.  Sometimes this argument can take on the aspect of religious zealotry. 

If community size is a religion, Vovici is agnostic.  Here are some of the advantages to a large community (400+ members):

• More members generate more discussion, making the site more compelling.
• The larger the community, the larger the segments, enabling targeted research of key demographics.
• Large communities become self-sustaining, needing very little outside direction or content seeding.

Here are some of the advantages of a small community (fewer than 400 members):

• The fewer members, the easier it is for a community moderator to direct the energies of the community.
• The exclusivity of small communities can make membership in such a community more attractive, with greater perceived value, than membership in an open community or large community.
• Small communities build an intimacy that leads to fuller disclosure and richer insights.  This is especially valuable for health-care related communities, where members discuss quite personal experiences with disease and chronic illness.

Both large and small communities have their value.  And both have their challenges.  The optimal size depends to a large degree on your purposes for building an online community in the first place.